It appears the first image -- the one that boots -- is likely from the alpha-6 load. I suspect you loaded alpha-6 at some point, right? If so, the root filesystem is also probably from the alpha-6 load as well, and thus compatible with the first kernel.

Where are the other two kernels from?

There are some changes to the root FS necessary that are necessary for another build of the kernel to work, although I don't know if it would hang the kernel not to have them present. There are also certain Uboot variables that need to be tweaked to accomodate certain kernels.

It's impossible to say what the root cause is from the information we have in this thread. I think rc3 probably has the best approach: Break out of the Uboot into the Marvell>> prompt and enter "printenv". Then post the results here, along with the lineage of the two kernels that hang.

It looks like the environment is basically from the alpha-6 load, with some additional modifications and additions thrown in afterwards.

You still haven't told us where the unbootable kernels come from, but I'm guessing #2 is one of the original kernels from Mavell. It may be necessary to set some different parameters for those, and I don't know what effect specifying arcNumber and mailineLinux will have on it.

FWIW, I've had good luck with the 2.6.30* kernels with the alpha-6 load's Uboot parameters. If you deviate much from that, I'm afraid I'm not going to be of much help.

So I go to ftp.kernel.org and get linux-2.6.30.3.tar.bz2 and linux-2.6.30.3.tar.bz2.sign. Do I expand this and rename the directory to linux-feroceon_4_2_7_KW? Can I then apply the Marvell LSP patch (linux-feroceon_4_2_7_KW.zip? And the big endian patch (0001_gw_BE-fix.patch)? What other patches are necessary to compile a kernel for the Sheeva Plug?